genesys: Add a way to override pixel coordinate divisor

backend/genesys/low.cpp

@@ -941,9 +941,12 @@ void compute_session_pixel_offsets(const Genesys_Device* dev, ScanSession& s,
     }
 
     s.pixel_count_multiplier = sensor.pixel_count_multiplier;
+    s.pixel_count_divisor = sensor.pixel_count_divisor;
 
     s.pixel_startx *= sensor.pixel_count_multiplier;
     s.pixel_endx *= sensor.pixel_count_multiplier;
+    s.pixel_startx /= sensor.pixel_count_divisor;
+    s.pixel_endx /= sensor.pixel_count_divisor;
 }
 
 void compute_session(const Genesys_Device* dev, ScanSession& s, const Genesys_Sensor& sensor)

backend/genesys/sensor.cpp

@@ -130,6 +130,7 @@ std::ostream& operator<<(std::ostream& out, const Genesys_Sensor& sensor)
         << "    dpiset_override: " << sensor.dpiset_override << '\n'
         << "    ccd_size_divisor: " << sensor.ccd_size_divisor << '\n'
         << "    pixel_count_multiplier: " << sensor.pixel_count_multiplier << '\n'
+        << "    pixel_count_divisor: " << sensor.pixel_count_divisor << '\n'
         << "    black_pixels: " << sensor.black_pixels << '\n'
         << "    dummy_pixel: " << sensor.dummy_pixel << '\n'
         << "    ccd_start_xoffset: " << sensor.ccd_start_xoffset << '\n'

backend/genesys/sensor.h

@@ -284,8 +284,10 @@ struct Genesys_Sensor {
     // CCD may present itself as half or quarter-size CCD on certain resolutions
     int ccd_size_divisor = 1;
 
-    // Some scanners need an additional multiplier over the scan coordinates
+    // This defines the ratio between logical pixel coordinates and the pixel coordinates sent to
+    // the scanner.
     int pixel_count_multiplier = 1;
+    int pixel_count_divisor = 1;
 
     int black_pixels = 0;
     // value of the dummy register

backend/genesys/settings.cpp

@@ -121,6 +121,7 @@ bool ScanSession::operator==(const ScanSession& other) const
         pixel_startx == other.pixel_startx &&
         pixel_endx == other.pixel_endx &&
         pixel_count_multiplier == other.pixel_count_multiplier &&
+        pixel_count_divisor == other.pixel_count_divisor &&
         conseq_pixel_dist == other.conseq_pixel_dist &&
         output_segment_pixel_group_count == other.output_segment_pixel_group_count &&
         output_segment_start_offset == other.output_segment_start_offset &&

backend/genesys/settings.h

@@ -283,8 +283,19 @@ struct ScanSession {
     unsigned pixel_startx = 0;
     unsigned pixel_endx = 0;
 
-    // certain scanners require the logical pixel count to be multiplied on certain resolutions
+    /*  The following defines the ratio between logical pixel count and pixel count setting sent to
+        the scanner. The ratio is affected by the following:
+
+        - Certain scanners just like to multiply the pixel number by a multiplier that depends on
+          the resolution.
+
+        - The sensor may be configured to output one value per multiple physical pixels
+
+        - The scanner will automatically average the pixels that come from the sensor using a
+          certain ratio.
+    */
     unsigned pixel_count_multiplier = 1;
+    unsigned pixel_count_divisor = 1;
 
     // Distance in pixels between consecutive pixels, e.g. between odd and even pixels. Note that
     // the number of segments can be large.
@@ -356,6 +367,7 @@ void serialize(Stream& str, ScanSession& x)
     serialize(str, x.pixel_startx);
     serialize(str, x.pixel_endx);
     serialize(str, x.pixel_count_multiplier);
+    serialize(str, x.pixel_count_divisor);
     serialize(str, x.conseq_pixel_dist);
     serialize(str, x.output_segment_pixel_group_count);
     serialize(str, x.output_segment_start_offset);